Two Texans were arrested Wednesday on federal charges they stole pieces of space shuttle Columbia that had dropped onto the countryside.

Federal officials in Texas also declared an amnesty period extending until 5 p.m. Friday, during which people who have collected shuttle debris can turn it in without fear of prosecution. After that, prosecutions will resume, they said.

Merrie Hipp, 43, of Henderson, was charged with theft of government property for allegedly stealing a shuttle circuit board on Saturday.

Bradley Justin Gaudet, 23, of Nacogdoches, was charged in a separate incident with stealing a piece of thermal insulating fabric. Gaudet is a student at Stephen F. Austin State University.

Both appeared in court later Wednesday handcuffed, shackled and with chains around their waists. They pleaded innocent and were freed on their own recognizance.

Neither suspect would comment, but their lawyers said both were unnerved by the charges, which carry a maximum of 10 years in prison and a fine of $250,000.

"The issue here is the thermodynamics of the space shuttle and any piece of that is important to this investigation," said U.S. Attorney Michael Shelby. "No one knows which piece will unravel the mystery."

Authorities said they are conducting at least 17 investigations into reports of people taking shuttle debris as souvenirs.

They would not give specifics or comment on whether those cases were related to attempts by people to sell purported shuttle debris on eBay.

"These two individuals are first," said U.S. Attorney Matthew Orwig. "There is no particular threshold. They are an example, whether it's our intention or not."

Authorities urged members of the public to take advantage of the amnesty period.

"If you turn the piece over and describe where you found the piece, we will not prosecute you," Orwig said.