MIDDLETOWN, Pa. (AP) _ Four days into the accident at Three Mile Island, the stream of conflicting statements was in full torrent.

The company, which had lost its credibility, said the crisis was over.

Minutes later, the Nuclear Regulatory Commission warned that a hydrogen bubble in the reactor was potentially explosive and blocked efforts to cool the uranium core.

The NRC in Washington feared the bubble could reach a flammable stage within five days.

NRC officials at the scene said detonation was impossible for at least nine to 12 days.

Scores of reporters, who carried radiation detection badges with their pads and pens, rushed the office of Gov. Dick Thornburgh. ''They were no longer interested in the story. They feared for their own safety,'' recalled former gubernatorial spokesman Paul Critchlow.

Reporters by trade are detached observers. But during the United States' worst commercial nuclear accident, they were as personally involved as the people who weathered the crisis.

The vanguard of a 400-reporter invasion was based in the state capital of Harrisburg 10 miles away, where a new governor was in his 71st day of office and the Legislature was debating the sorry condition of the state's roads.

Three Mile Island overwhelmed everyone. And reporters found out fast that it was a nightmare of confounding technology, contradictions, feverish emotions and limited access to sources.

It took seven days to get a clear story from all involved, when the NRC confirmed the hydrogen bubble was gone and gave a plain account of what happened. Everything before seemed disjointed.

The near-calamity lacked such visuals as fire, funnel clouds, floodwaters or wreckage. The most popular image was the looming presence of the huge, hourglass-shaped cooling towers.

Reporters had to learn quickly about the extremely complex workings of a nuclear-powered generating system.

At 4 a.m. on March 28, a Wednesday, Three Mile Island worked like a giant tea kettle making steam for electricity from its hell-fired reactor. Then a balky valve caused two pumps to shut off, which halted a steam turbine and stopped the chain reaction within the reactor.

One hundred tons of uranium sizzled with decay heat, and a relief valve opened to reduce pressure as the emergency cooling system flooded the reactor with water. But the valve stuck and stayed open for two hours, draining vital coolant water and leaking radiation into the air.

Operators looking at a faulty gauge mistakenly shut off the emergency cooling system. The core was uncovered and the top half melted. A bubble of hydrogen formed.

But at the time, no one had a clue what was going on.

Nothing in operator manuals mentioned a bubble. It was as if operators were given history books to take an algebra test. A computer measuring core temperatures spit out question marks, the high-tech equivalent of scratching your head.

The nuclear industry, which touted itself as cleaner than coal and cheaper than oil, had bragged such an accident was impossible. And the company's operator then, Metropolitan Edison Co., played down the gravity of the situation.

The first word from Metropolitan Edison came from its headquarters in Reading, 55 miles away. ''There have been no recordings of any significant levels of radiation, and none are expected off site,'' spokesman Blaine Fabian said.

Lt. Gov. William Scranton III reassured reporters at an 11 a.m. briefing that ''everything is under control.'' Unknown to him or reporters, the plant was venting radioactive steam at the time.

An angry Scranton returned at 4:30 p.m. to say: ''Metropolitan Edison has been giving you and us conflicting information.''

Asked why reporters were not told about the venting, Metropolitan Edison vice president Jack Herbein said, ''They didn't ask.''

But the company wasn't alone in rosy statements. A Nuclear Regulatory Commission staffer said the accident ''wasn't close to a catastrophe.''

The next day, Metropolitan Edison President Walter Creitz said the plant was safely shut down. In reality, it was leaking radioactivity and staying stubbornly hot.

All trust disintegrated with a new burst of radiation Friday, which prompted the public to flee a nuclear reactor for the first time.

Mothers left dishes in the sink and clothes in the washer after Thornburgh advised pregnant women and young children within five miles of the plant to leave. An unauthorized Civil Defense siren wailed eerily in Harrisburg.

''We are operating almost totally in the blind,'' NRC Chairman Joseph Hendrie said that morning. ''It's like a couple of blind men staggering around making decisions.''

One neighbor seeking answers telephoned to ask a reporter about the newsman's wife and two children. Told they had gone to visit relatives, the neighbor hung up without a good-bye. Then her car was heard speeding away.

A reporter could cover a Metropolitan Edison news conference at American Legion Post 594, head down the street to hear the NRC and then drive back to Harrisburg to get the state version.

At one of these antsy sessions, with reporters shouting questions while standing on folding chairs, Herbein said: ''I don't know why we need to tell you each and everything we do.''

Desperate for facts, Thornburgh sought White House help. It sent as its spokesman Harold Denton of the NRC, whose soothing Southern drawl and grasp of reactors helped calm things down.

The White House also put a gag order on Metropolitan Edison so only one story would come out. President Carter visited on Sunday, to reassure a jumpy populace while technicians worked to remove the bubble.

Metropolitan Edison said the bubble was gone the next day. A company official repeated the news over the phone to four reporters before they felt comfortable with the information.

The NRC confirmed Tuesday that the bubble was gone and six days later declared the crisis over.

There were interviews with jittery residents who had radiation badges hanging on shrubs with the springtime's first buds.

In an area where the peaceful Amish still use plowhorses as pre-industrial tractors, Middletown Mayor Robert Reid ordered his police to shoot looters.

A church service in the Susquehanna River town of Goldsboro drew four worshippers monitored by a reporter and two photographers.

Then came salt and pepper shakers shaped liked cooling towers, store signs of ''We don't sell Pennsylvania milk,'' and weather jokes about it being partly cloudy with a 40 percent chance of survival.

The swarm of out-of-town media found this note from the locals in the newsroom of the state Capitol:

''If you must go out on the streets of Harrisburg and see they are dark and empty, this is not - repeat not - because of the accident at Three Mile Island. That's the way they always are.''