WASHINGTON - The Obama administration asked BP Plc Thursday to make public detailed information about the Gulf oil spill including all measurements of the growing leak, sampling of air and water quality, trajectories of underwater plumes and locations of dispersants.

At the same time, the Environmental Protection Agency has directed oil giant BP to use a less toxic form of chemical dispersants to break up the oil spill in the Gulf of Mexico.

In a notice to BP, the EPA said that while it initially approved the current dispersant being used, much about the effects of the chemical remains unknown. One of the chief agents being used, called Corexit 9500, is identified as a "moderate" human health hazard that can cause eye, skin or respiratory irritation with prolonged exposure, according to safety data documents.

The request followed growing criticism from scientists that BP is drastically underestimating the size of the leak - and that government agencies aren't doing enough to pressure the company to be transparent and allow independent reviews.

"In responding to this oil spill, it is critical that all actions be conducted in a transparent manner, with all data and information related to the spill readily available to the United States Government and the American people," Homeland Security Secretary Janet Napolitano and Environmental Protection Agency Administrator Lisa Jackson wrote to the company's chief executive, Tony Hayward.

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The letter asks for a website address to be provided to the government within 24 hours with sampling plans and work plans.

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Within 48 hours, the company is asked to post a large range of environmental and analytical data in detailed form.

For weeks BP has said the flow is 210,000 gallons a day, but scientists say the amount could be much higher. A BP official conceded Thursday there could be more.

BP officials did not immediately respond to a message seeking comment.