Local environmental officials throughout the Gulf Coast are feverishly collecting water, sediment and marine animal tissue samples that will be used in the coming months to help track pollution levels resulting from the Deepwater Horizon oil spill.

Hundreds of millions of dollars are at stake, since those readings will be used by the federal government and courts to establish liability claims against BP. But the laboratory that officials have chosen to process virtually all of the samples is part of an oil and gas services company in Texas that counts oil firms, including BP, among its biggest clients.

Some people are questioning the independence of the Texas lab. Taylor Kirschenfeld, an environmental official for Escambia County, Fla., rebuffed instructions from the National Oceanic and Atmospheric Administration to send water samples to the lab, which is based at TDI-Brooks International in College Station, Tex. He opted instead to get a waiver so he could send his county’s samples to a local laboratory that is licensed to do the same tests.

Mr. Kirschenfeld said he was also troubled by another rule. Local animal rescue workers have volunteered to help treat birds affected by the slick and to collect data that would also be used to help calculate penalties for the spill. But federal officials have told the volunteers that the work must be done by a company hired by BP.