At least 106 chemical plants and as many as 111 plants nationwide could be targeted by terrorists for attacks causing toxic explosions that could result in up to one million casualties, according to a new report by congressional researchers.

The report comes as the Homeland Security Department considers tougher federal regulation of the chemical industry, which has largely policed its own security procedures.

The American Chemistry Council, an industry group long opposed to any federal security regulations, dropped opposition to the federal regulatory approach earlier this year, when it became apparent that several states might pass chemical security laws, creating the danger of a confusing patchwork quilt of laws.

The survey of plants possessing large amounts of 140 toxic and flammable chemicals was compiled by the Congressional Research Service using EPA data from May, the most recent available.

The survey provided state-by-state figures for chemical plants located near populations of over one million but did not specify the names of the facilities or the cities in which they are located.

Up to 29 of the plants were located in Texas — more than twice as many than in any other state. Illinois and California each had up to 13 such plants, Ohio had eight, and Florida and New Jersey had seven apiece.

EPA refuses to release its own list of detailed locations of the chemical manufacturing plants, oil refineries and storage facilities for fear doing so could aid terror plans.

Experts said the number of injuries or deaths caused by emissions of chemical explosives or toxic gases would depend largely on unpredictable factors like wind current or the extent of the leak. But they agreed the report highlights the continued danger of questionable security practices at plants.