CAMERON, Mo. -- A former manufacturing plant is the new focus of an investigation into a high number of brain tumor cases in Cameron.

Missouri and federal environmental officials took ground and water samples from the former Rockwool Industries plant Monday and Tuesday. They found no unusual levels of contaminants with hand-held devices but the material will be tested further in laboratories, said David Bryan, a spokesman for the Environmental Protection Agency in the Kansas City region.

The results should be known around Aug. 1, he said.

Some Cameron residents have said that at least 11 residents have developed brain tumors since 2002. At a community meeting in early July, officials from the state's cancer registry said that they have received reports of 20 to 40 other cases, although those reports have not been verified.

Investigators are trying to determine if there is a single cause for the tumors.

Rockwool, four miles west of Cameron, converted iron into fiber insulation for buildings before closing more than 20 years ago. The plant dumped residue from the iron product next to the plant and at a quarry three miles away. No allegations of illegal dumping have been made.

The site is hooked into the city water system.

The EPA and the Missouri Department of Natural Resources took samples of the residue, called slag, and of stone, soil and water from waste sites at Rockwool.

Federal and state investigators tested Cameron's drinking water in May and said it met health standards.

Cyndee Gardner, whose 8-year-old daughter, Maycee, was diagnosed in late May with two benign brain tumors, said she is glad the tests are being done, even if they don't provide answers to the illnesses.

"I'll be fine with whatever they find," Gardner said.

The city bought the building and leased it to a coat-hanger manufacturer from 1992 to 2003.

The Rockwell site is now used by Sukup Manufacturing Co. as a distribution center for material used in construction of silos and other buildings.

Roger Hill, Sukup manager, said Tuesday that he doubted that the old Rockwell plant is a health hazard two decades after it closed.