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MIAMI (CBSMiami) – A day after Miami Dade County Mayor Carlos Gimenez announced he had launched an investigation into what he termed “bus safety issues,” the chairman of the commission’s transportation committee said he would initiate his own review of the transit department.

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“We need to find out what failed here,” said Miami Dade County Commissioner Esteban Bovo, adding the transportation committee would begin pressing for answers at its meeting next Wednesday

The flurry of activity follows a CBS4 News investigation into the death of bus driver Laquita Alvin, who was run over and killed by her own bus on December 5. Alvin had failed to engage the parking brake before getting off her bus, but CBS4 also discovered that a critical warning system on her bus was broken.

The warning system, known as a seat alarm, would have alerted Alvin the parking brake was not properly set as soon as she got out of her seat.

Documents obtained by the station revealed hundreds of other buses also had broken or disabled seat alarms. In all, 92 percent of the seat alarms installed on the buses were not working at the time of Alvin’s accident.

“If it’s a maintenance issue, if it’s a budgetary issue that we were not asked to address, a runaway bus issue,” Bovo told CBS4’s Jim DeFede. “Then obviously somebody has to answer for that.”

CLICK HERE to watch Jim DeFede’s report

Bovo said the new revelations surrounding Alvin’s death are deeply disturbing.

“I can’t fathom for a second that Miami Dade County is putting out equipment that could end up costing not only the lives of the operators, but the lives of some of the residents who may be using it,” he said.

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As it becomes increasingly clear Alvin would be alive today if the seat alarm was working, county officials are scrambling for answers. Following the initial CBS4 News report, the mayor announced he was launching an investigation to determine if the broken alarms were due to acts of vandalism – raising the possibility that it may be the drivers themselves who are disconnecting the alarms.

He reiterated that message on Thursday, issuing this statement to CBS4 News:

“On Monday, I ordered an investigation into the safety issues surrounding Miami-Dade County Transit buses. This week MDT sampled 35 buses and found that 57 percent of them had alarms that had been disconnected, not broken.”

“At this time it is unclear why such a high number of seat alarms are being manually disconnected. The County is investigating further.”

“It is the responsibility of the maintenance workers to inspect these safety devices every 6,000 miles. We will review the records to ensure that they fully complied with their duties. We will also make it abundantly clear to all of our personnel that tampering with safety devices will not be tolerated. Anyone caught doing so, will face disciplinary action up to and including dismissal.

“While these seat alarms as well as the decals placed in the bus operator’s compartment are an additional reminder for bus operators to follow procedure, bus operators also receive extensive training throughout the year on how to accurately secure their vehicles and avoid tragedies like this.”

The bus driver’s union reacted angrily to the allegations. Clarence Washington, president of the Transportation Workers Union, Local 291, issued a statement:

“Our transit employees are incredible professionals who put safety first. The Mayor’s false accusations are disrespectful to the dedicated employees of the County. The Mayor and his transit director continue to fail our citizens through their lack of leadership and by consistently blaming others for their own failures.”

Bovo said he just wants to get to the truth.

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“At the end of the day it’s the commission that holds the bag on these kinds of things and has to respond to it,” he said.

Jim DeFede