HOUSTON (AP) — At least 2 tons of highly unstable chemicals used in such products as plastics and paint exploded and burned at a flood-crippled plant near Houston early Thursday, sending up a plume of acrid black smoke that stung the eyes and lungs.

The blaze at the Arkema Inc. chemical plant burned out around midday, but emergency crews continued to hold back because of the danger that eight other trailers containing the same compound could blow, too.

No serious injuries were reported. But the blast added a new hazard to Hurricane Harvey's aftermath and raised questions about the adequacy of...