Casey Kuhn/KJZZ

The sign outside of Hickmans Family Farms in Buckeye, Arizona.

It’s a twist on a classic question: What came first – the town of Tonopah or the egg-laying facility next to it?

Tonopah is an unincorporated area west of Buckeye where local egg production company Hickman's built a huge egg facility in 2014. It houses over 4 million chickens, and locals have opposed it since the beginning, saying the ammonia odors and other emissions have threatened health and livelihood.

Hickman's President Glenn Hickman said his business follows all rules and regulations.

“We don’t really think there’s an end to this. We’ll continue to be harassed by the neighbors, and we’ll continue to have to respond,” Hickman said.

Most recently the Environmental Protection Agency filed a letter in June to Hickman's checking its compliance with the Clean Air Act (CAA) at the Tonopah and Arlington facilities.

In the letter, the EPA asks for information from Hickmans such as, total monthly production of compost and fertilizer per month from January 2011 through May 2016. It also asks for a list of power generating equipment, air quality permits, and specifics on how the Hickman's hen houses are operated.

Neither the EPA nor Hickman would comment on particulars of the ongoing investigation.

Socially Responsible Agriculture Project Director Danielle Diamond helped file an initial complaint to the EPA about the facilities, and said the agency did not have to respond to the complaint this way. She thinks it shows the locals’ concerns are real.

“And in this particular case we have an extremely large operation that is impacting people in the community," she said. "So that might be another reason EPA is looking at it.”

Diamond said the EPA doesn't usually file CAA investigations against agriculture facilities because of a livestock emissions study that had been going on for years.

Hickman's has had three EPA information requests, with two in the last five months related to the CAA

In 2004, the EPA fined a large egg producer in Ohio more than $880,000 for violating the CAA.

Maricopa County Board Supervisor Clint Hickman, related to the business, does represent the area his family's egg business operates, but recuses himself when Hickman's Family Farm issues come before the board.

EDITOR'S NOTE: The story was updated to reflect previous information requests from the EPA to Hickman's.