(Reuters) – Water samples collected after an Arkema chemical plant in Crosby, Texas caught fire following a power outage due to Tropical Storm Harvey contained no volatile chemicals, the U.S. Environmental Protection Agency said Friday.

The Arkema plant experienced a series of fires as a result of sensitive organic chemicals that rose to dangerous temperatures after the facility lost power due to storm flooding.

People in a 1.5-mile radius around the plant, located about 20 miles (35 km) northwest of Houston, were evacuated after company officials said an explosion or large fire was likely because the organic peroxides used to make plastics and other products could not stay cool enough.

The EPA, in its statement, said that no “volatile organic chemicals or semi-volatile organic chemicals were detected in the surface water runoff samples,” which were collected on September 1.

The investigation, which involves the U.S. Chemical Safety Board, the Texas Commission on Environmental Quality, and other state, federal and local agencies, is ongoing.

The first explosion took place on Aug. 31, several days after Harvey hit. The storm dropped several feet of rain in the Houston area.