CHICAGO (CBS) — Volunteers were loading three tractor trailers with bottled water on Wednesday, so it could be shipped to Flint, Michigan, to help residents dealing with a water crisis.

Sweet Holy Spirit Church in the South Chicago neighborhood held a seven-day drive to collect bottled water for the people of Flint. The tap water in Flint has been contaminated ever since the city switched from Lake Huron water supplied by Detroit to water from the Flint River in 2014.

The highly polluted water in the Flint River damaged pipes, and caused lead to leach into the water.

That led to the poisoning of an unknown number of children and other residents. Flint has since switched back to Lake Huron water, but residents fear the previous damage to the pipes continues to cause lead to leach into the water.

Members of Sweet Holy Spirit Church in Chicago have collected 160,000 bottles of water for Flint. On Wednesday, they will load the water onto three trucks to ship the water to Flint.

The pastors behind the water drive said their congregations take what happened in Flint personally.

“This is a national crisis. Flint has well over 100,000 residents; and with indigents, those who live below the national poverty line, seniors, and common people who right now are trapped, and they don’t have a place to turn, anybody to turn to. Help is on the way from Chicago,” said Bishop Tavis Grant, pastor of Greater First Baptist Church.

At 8 a.m. Wednesday, the U.S. House Oversight Committee will hold hearings examining the water crisis in Flint, to determine exactly what went wrong. Also, the FBI has announced it is joining an ongoing investigation to find out if any crimes were committed by Michigan or local officials in charge of Flint during the crisis.

The switch was made at the behest of an emergency manager appointed by Michigan Gov. Rick Snyder, after the state took control of financial decisions in Flint.