PHILADELPHIA — The federal corruption case against state Sen. Vincent Fumo grew stronger Tuesday as a second computer technician admitted he destroyed evidence as the FBI closed in on the Philadelphia power broker.

Mark Eister, 38, of Camp Hill, pleaded guilty Tuesday to five obstruction-related counts, acknowledging that he systematically destroyed e-mails from Senate computers in Harrisburg.

Eister and fellow technician Leonard Luchko, who pleaded guilty earlier this month, have both agreed to testify against Fumo at his upcoming trial, which starts Sept. 8 in Philadelphia.

Fumo lawyer Dennis Cogan has not commented on the co-defendants' pleas and did not return a message left Tuesday by The Associated Press.

Prosecutors say Eister and Luchko worked "exhaustively" to destroy e-mail evidence for Fumo as the FBI investigated whether he extorted $17 million from Peco Energy for a neighborhood nonprofit group run by his former staffers.

The nonprofit, Citizens Alliance for Better Neighborhoods, worked on street cleaning and ran a charter school in South Philadelphia. But prosecutors say Fumo also used the group's coffers as his own, spending $600,000 of charity funds to furnish his district office, renting campaign space free and using staff for countless personal and political chores.

Fumo's sole remaining co-defendant is Ruth Arnao, a friend who ran the nonprofit.

Fumo and others misused $1.4 million from Citizens Alliance, as well as $100,000 from the Independence Seaport Museum and nearly $2 million from the state Senate, prosecutors said in court documents filed this week.