HOUSTON, Aug. 30 (Xinhua) -- Hurricane Harvey has downgraded to a tropical depression, but heavy rains could still cause new flooding in far eastern Texas and western Louisiana, the National Hurricane Center warned on Wednesday.
At least 30 people were dead or feared dead in flooding triggered by the tropical storm, local officials said.
Medical examiners are confirming the death toll from the historic flooding as efforts to search for the missing people continue.
By midday Wednesday, more than 40 people had been arrested for looting in Houston and surrounding areas.
A citywide curfew which remains effective from midnight to 5:00 a.m. (1000 GMT) helps to keep the criminals at bay, Houston Mayor Sylvester Turner said Wednesday.
The two dams of Addicks and Barker seemed safe without immediate danger of failing. Rising water levels in the two reservoirs are spilling over into adjacent subdivisions that sit against the dams.
Officials said that thousands of homes are at risk of flooding and evacuation orders have been issued for at least 80 subdivisions.
Meanwhile, a chemical plant struck by Harvey is likely to explode.
The Arkema chemical plant in the city of Crosby, northeast of Great Houston, was knocked out power by floodwaters on Monday. The plant needs electricity to keep volatile chemicals stored at the facility cool.
Rich Rowe, CEO of Arkema, told the press that if the volatile organic peroxides stored at the plant get too warm, some sort of explosion will be inevitable.
Flights into and out of Houston resumed Wednesday evening, with a limited number of domestic flights. The international airport of Houston was shut down on Sunday.
At the state's Emergency Operations Center, Governor Greg Abbott announced on Wednesday that the number of National Guard troops assisting with the storm's aftermath will increase to more than 24,000 in coming days, 10,000 of whom are from other states.
As water begins to recede in Houston, officials warn residents about potential health risks.
They are advised to stay vigilant to flood water which could have dangerous debris, downed power lines and snakes, and to remove standing water to reduce the threat of mosquito-born diseases.