HELENA, Mont. (AP) — Montana authorities ordered the evacuation of 60 homes Tuesday as the rising Clark Fork River submerged a neighborhood west of Missoula and potentially threatened hundreds of additional residences.

The Missoula County Sheriff's Office issued the evacuation order for the houses and trailers closest to the river in the Orchard Homes neighborhood in the state's second-largest city. Authorities have set up a shelter at a Missoula church and asked people who leave their homes to check in with the sheriff's office.

Just a day earlier, sheriff's deputies went door to door in the neighborhood to warn people of possible evacuations. Sheriff's spokeswoman Brenda Bassett said she didn't know how many people left as a result of those warnings — or how many are likely to defy the order.

"We don't have a gauge of that just yet," she said.

The river has been rising for days as the near-record snow high in the mountains surrounding the city melts in the warm spring weather. The Clark Fork is at moderate flood level and is expected to keep rising until Friday, with forecasters predicting it will surpass 13 feet (3.96 meters) for only the sixth time in recorded history.

If that happens, the flooding could affect at least 800 homes from eastern Missoula to west of the city where the Clark Fork meets the Bitterroot River.

Bassett said there is no timeline to expand the evacuation order.

Outside Helena, water from the flooding Tenmile Creek has entered an unknown number of homes, Lewis and Clark County emergency coordinator Reese Martin told Gov. Steve Bullock in a briefing Tuesday.

Martin said officials have handed out 38,000 sandbags as residents in the valley use them to line roads and encircle homes and a school that are threatened.

County officials have rented two 8-inch (203-millimeter) pumps to divert some of the water, which has contaminated at least one well in a trailer and RV park, Martin said.

The Flathead and Yaak rivers in northwestern Montana are also threatening to spill from their banks and cause minor flooding near Columbia Falls and Troy, according to the National Weather Service.

Most rivers are expected to crest Thursday and Friday, but the flooding around Missoula is expected to continue for a week or longer, according to the weather service.