(Reuters) - Floods across the U.S. Midwest that have killed at least five people shut major roadways in the St. Louis area on Wednesday, while residents of vulnerable areas piled sandbags to avert destruction as rivers were expected to crest.

The flooding was caused by a storm that parked over the region last weekend and dumped almost 12 inches (30 cm)of rain, the National Weather Service said.

A faster-moving storm was expected to drop up to 5 inches (13 cm) more rain on Wednesday on already saturated parts of central and southern Missouri, southern Illinois, northern Arkansas, central Indiana and Oklahoma.

“Today adds insult to injury,” said NWS meteorologist Bob Oravec. “When you see rivers flooding and it’s still pouring, it can zap the spirit. This is additional bad news.”

The flooding along the Mississippi River and Ohio River is the worst since late 2015, he said.

Five people were killed by flooding in Missouri, the last two of them swept from their cars on Monday and Tuesday, said NWS meteorologist Brian Hirsch.

More than 300 roads were closed over portions of the Midwest, including Interstate 44 in St. Louis, which may remain closed through Saturday, he said.

“You find your road is filled with water, find another way. When you press through that intersection, you are really are pressing your luck,” Hirsch said.

Amtrak suspended rail service across Missouri. The U.S. Coast Guard closed the Mississippi River to all traffic near St. Louis.

Hundreds of residents in Eureka, Missouri, piled high walls of sandbags to guard their homes from the rising Meramec River in suburban St. Louis, said Mark Diedrich, director of the St. Louis County Office of Emergency Management.

Mandatory evacuations in levee-protected areas of nearby Valley Park were ordered by Mayor Mike Pennise. National Guard helped volunteers stack sandbags, although 200 homes have already been damaged by floodwaters and another 1,500 are threatened, Diedrich said.

“We are getting about 4 inches (10 cm) of rain today and tomorrow which (may) keep the river out of its banks longer,” Diedrich said in an email.

Most of the rivers across the U.S. Midwest were expected to crest over the weekend, NWS meterologist Oravec said. In the St. Louis area, the Mississippi River was forecast to crest on Friday.

“The rain is coming to an end but the rivers are still filling,” he said.