Only one-third of voting precincts in Prince George's County were provided with as many voting machines as required by law on Election Day, a failure that might have caused long lines that frustrated many residents, a state analysis has concluded.

In a letter sent to the county's Board of Elections last month, State Elections Administrator Linda H. Lamone wrote that the county provided too few voting machines at 133 of the county's 206 precincts, and she asked for an explanation. State law requires one machine for every 200 registered voters.

Long lines were common Nov. 7 at many Prince George's polls, where some voters waited until midnight.

One voting station, at the University of Maryland, was supposed to have 12 machines but was provided with four. On Election Day, students did not finish voting until 2 1/2 hours after the polls closed.

In her letter, released publicly yesterday, Lamone wrote that the insufficient number of voting units was "most likely the primary cause" for the lines.

In response, county elections officials acknowledged in a letter to Lamone that they failed to provide enough machines in many precincts. The waits caused by the error were compounded by a long ballot that included 13 local questions.

"People stewed over the questions. Some were there for 15 minutes," said Board of Elections President S. John di Stefano.

Interim Elections Administrator Robert J. Antonetti Sr. said the machine error occurred because an employee missed a summer deadline to provide voter registration information to the state. As a result, machines were apportioned using voter registration data from 2004 instead of updated figures. The employee was overwhelmed with work and is no longer employed by the county, Antonetti said.

"It's extremely disappointing," di Stefano said. "We just hope to heck it never happens again."