By KYLE POTTERST. PAUL, Minn. (AP) â¿¿ Minnesota lawmakers began drilling into the state's silica sand mining Tuesday with hours of testimony from advocates and opponents, the first phase of a potential fight over what role the state should play in overseeing the booming industry. Critics came by the busload to the Capitol for a joint hearing of the Senate and House environment committees. One by one, concerned citizens from southeastern Minnesota asked lawmakers for a statewide study of health and environmental impacts; a temporary moratorium on new mines and processing facilities; and establish better statewide oversight and regulation. So far, the issue has been left to local governments. Representatives from companies that run silica mines in Minnesota said state regulation would be too much of a burden, and said city and local governments can better oversee silica mining in their own backyards. "We feel they are the best suited to decide the local land issues," said Mike Caron, director of land use affairs for Tiller Corp., which recently got permits from North Branch to build a sand drying facility. "They are each unique, and each of them should be studied on their own so that all of the local issues and concerns can be dealt with." Democratic Sen. Matt Schmit of Red Wing said after the hearing that he plans to introduce a bill Thursday that would broaden the state's oversight and call for a study. Sen. John Marty, a Roseville Democrat and chair of the Senate Environment and Energy Committee, backs that proposal. He said a statewide study may require putting a hold on permits for new mines. Schmit's bill may get a hearing as soon as next week. "There are so many unknowns. Rather than blindly go ahead, let's make sure we do it right," Marty said.