A recent investigation into Colorado’s voter rolls found that dead men and women had fraudulently cast votes in multiple state elections.

CBS4 reported multiple cases of voter fraud after the station compared voting histories in Colorado with a federal death database.

“We do believe there were several instances of potential vote fraud that occurred,” said Colorado Secretary of State Wayne Williams to CBS4. “It shows there is the potential for fraud.”

One of the biggest voter fraud cases the station found was through the voting record of Sara Sosa of Colorado Springs. She died October 14, 2009, but ballots were cast in her name in 2010, 2011, 2012, and 2013.

Her husband died on September 26, 2008, but a ballot was cast in his name in 2009.

“Somebody was able to cast a vote that was not theirs to cast,” El Paso county clerk and recorder Chuck Broerman told CBS4, saying that the problem of people voting on behalf of the dead is “very serious.”

Broerman said the Sosas remained active on voter rolls because they did not meet the criteria to have their names removed from the rolls.

According to CBS4, state voting officials can only strike names from voting rolls if names, dates of birth, and addresses match the voting record. If there are errors, election officials leave deceased people registered, leading to fraudulent votes.

Following CBS4’s investigation, the Colorado Secretary of State’s office confirmed that at least 78 dead people are registered to vote.

In May 2016, California found that it had hundreds of dead voters on its voter rolls, with 215 of them in the Los Angeles County area alone.