Hurricane Harvey’s floodwaters triggered a spill of almost a half-million gallons of gasoline from two storage tanks along the Houston Ship Channel, marking the largest spill reported to date from a storm that slammed into the heart of Texas’ huge petrochemical industry.

The spill measured 10,988 barrels, or more than 461,000 gallons, and occurred at a petroleum tank farm in Galena Park operated by Magellan Midstream Partners, according to the Oklahoma-based company and accident reports submitted to federal officials.

Some of the spilled fuel flowed into a waterway adjacent to the ship channel, a heavily-industrialized area that’s lined with dozens of petrochemical facilities, the reports said.

Gasoline is more volatile than oil, meaning it evaporates more quickly after it’s spilled. But it’s also more likely to catch fire than oil and can more rapidly penetrate the soil and potentially contaminate groundwater supplies.

Magellan spokesman Bruce Heine said the gasoline that reached the small, unnamed waterway had been contained. The spilled fuel was sprayed with foam to prevent it from releasing harmful vapors, he said.

“Federal and state regulators have been on-site during the recovery and clean-up procedures,” Heine said. “Clean-up activities at the facility are continuing and we are currently removing and replacing affected soil.”

The Texas Commission on Environmental Quality (CEQ) and the U.S. Environmental Protection Agency were unable to immediately answer questions about possible health effects and environmental contamination from the spill.