The owner of a flooded-out chemical plant in Crosby, Texas, said early Thursday it received reports of explosions at the plant.

Arkema Inc. said the Harris County Emergency Operations Center notified the company at 2 a.m. Thursday of explosions and black smoke coming from its Crosby plant, which was inundated by Hurricane Harvey’s floodwaters.

But the Harris County sheriff Thursday morning described the incident as a chemical reaction, not an explosion.

The development comes a day after Arkema, whose chemicals are used in making plastics, warned that the organic peroxides used in the site’s manufacturing process had begun to heat up after the plant lost its primary source of power and backup power from generators. Without electricity to power refrigeration, the chemicals — stored in 18-wheeler box vans throughout the plant — were expected to degrade, possibly leading to some type of explosion or fire.