HOUSTON (Reuters) - Thirteen Superfund sites, heavily contaminated former industrial zones, in Texas were flooded or damaged by Hurricane Harvey, but the full impact on surrounding areas was not immediately clear, the U.S. Environmental Protection Agency said on Saturday.

The announcement came amid rising concern about the health risks posed by Harvey’s record floodwaters, which contain a toxic soup of chemicals, oil and bacteria from Houston’s notoriously leaky sewer system.

The EPA said it found the flooded or damaged Superfund sites using aerial images but had been able to physically inspect only two of them so far. Neither of those two require emergency cleanup, EPA said.

Reaching the 11 other Superfund sites could take time, however, because floodwaters have yet to fully recede.

“Teams are in place to investigate possible damage to (the other 11) sites as soon flood waters recede, and personnel are able to safely access the sites,” EPA said.