An explosion sent flames 30 feet into the air in University City Wednesday and within minutes, a few miles away, a downed wire landed across a major San Diego highway injuring at least two people.

San Diego Gas & Electric and San Diego firefighters responded to reports of an explosion and flames near Greenwich Drive and Governor Drive around 9:50 a.m. Wednesday.

Witnesses described it as a "mini sonic boom" - loud enough to peak curiosity but not frightening. Firefighters initially reported the explosion as a transformer fire.

Meanwhile, California Highway Patrol officers were called when a power line fell across all lanes of State Route 52 between Interstate 805 and Genesee.

The static line broke with the transformer disruption and fell into oncoming traffic. One vehicle traveling westbound was damaged when the car struck the wire described as 3/8 inch of steel cable.

A big rig hit the top of the wire and spooled the wire over.

Pieces of the aviation ball were left in the median of the highway.

Cindy Bassuk was driving along the highway when she saw something she's never seen before.

"The ball coming down and the line coming with it, then the second ball coming down," Bassuk said.

There was a crash involving a vehicle in the eastbound lanes, one driver was transported to the hospital. Another woman who was riding in a car at the time said she was suffering pain and will seek medical attention.

Jamie Page, Director of Facilities at Mitchell International, a software development company on Greenwich Drive said SDG&E crews have been working on a controlled natural gas release for a couple of weeks.

“I think what happened is the wind shifted, and it caused an arc of flame to go up through up through the muffler,” Page said. “The top of the flame hit an electrical wire and then I think the wire caused a surge of power to go down the line a little bit."

Another person working in the area described the explosion as a fireball.

“I looked out the window and saw a fireball maybe the size of a truck, felt the heat and the fireball after a few seconds went down to just a small flare,” said Oracle Database Administrator Joseph Rodriguez.

San Diego police say they've received several reports from the public reporting flames.

Lynn Mulvut Connot posted on NBCSanDiego's Facebook page "Oh yeah, it was a big one... the flames shot 30 feet into the air. You could see it from our conference room here at the office."

There were approximately 10 SDG&E vehicles at the location near Greenwich and Governor however SDG&E told NBCSanDiego the company had not received a report of a transmitter fire.

“We are investigating, trying to figure out exactly what happened,” SD&E spokesperson Erin Koch said. “We’re trying to track down what caused the explosion “

Two hours after the incident, Hanan Eisenman with SDG&E confirmed there was a “brief ignition” at the Greenwich and Governor location where crews were conducting “routine maintenance” but could not confirm if the spark at the pipeline caused the incident along SR-52.

No customers were hurt.

San Diego police spokesperson Lt. Andra Brown and San Diego Fire spokesperson Maurice Luque said a crane owned by private company struck nearby power lines.

However, an SDG&E spokesperson told NBCSanDiego no crane was involved.

Crews initially warned Page to stay clear of the area because they were concerned electrical lines may fall on several parked cars.

All 900 employees working in the office building near the transformer have been notified of the threat via email.

Power in the area is up and running.

Check back for updates to this developing story.

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