WASHINGTON, D.C. -- Federal regulators launched a broad effort in May to study and police how the growing number of cell phone and broadcast towers sprouting across the country affects historic sites, Indian land and the environment, according to the Associated Press.

FCC Michael Powell told AP his agency will work with the U.S. Fish and Wildlife Service to study why migratory birds fly into towers. An estimated 5 million to 50 million birds die in such accidents each year, according to Fish and Wildlife.

"I know there's a problem, and towers are one of the possible causes," Powell said. "We don't know exactly how or why."

Researchers theorize that lights on the towers attract the birds. Powell said more research is needed to understand the problem and the role of lights and tower height and design. He added that the new plan is the FCC's first comprehensive effort to protect the environment and historical sites while speeding the installation of communications equipment. The FCC plans to hire more staff, improve cooperation with industry, toughen enforcement of environmental rules and possibly change regulations.

However, the cell phone industry is worried. Tom Wheeler, president of the Cellular Telecommunications & Internet Association told AP that dead spots and dropped calls can only be eliminated by new cell sites. "Government actions that delay or complicate the process of building a more robust network for our consumers are particularly unhelpful," he said.

Powell said the FCC also would work to ensure that American Indian tribes are consulted when towers are proposed for sites that might have historic, cultural or religious significance.

There are more than 100,000 communications towers in the United States, including antennas for cell phone signals and television and radio broadcasts, according to the FCC. The vast majority of those towers is taller than 200 feet and has lights to prevent aircraft collisions.

Several environmental groups are suing the FCC over communications towers near the Gulf of Mexico, where many birds stop during spring and fall migrations. The groups want the FCC to review the danger to birds before towers go up and keep birds away from existing towers with devices like noisemaking machines.