10News' Joe Little reported ATF agents are speaking with residents in the area to find out if they have witnessed any suspicious activity around the neighborhood prior to Thursday's blast

Sheriff's department spokeswoman Jan Caldwell declined to disclose further information about the device, including whether it had been planted in or on the truck, or positioned on the roadway beneath it. No suspects have been identified, she said.

The explosion happened shortly after 4:30 p.m. in the 12000 block of Via Hacienda near Cuyamaca College.

According to the sheriff's department, 52-year-old Connie Hoagland turned on the ignition in her truck and it exploded. The blast threw the truck back 40 feet and Hoagland rolled out from the vehicle. She was severely injured in the incident, and after life-saving measures were performed at the scene Hoagland was taken to UCSD Medical Center to undergo surgery.

10News learned Hoagland, a Rolando resident, suffered two broken legs in the blast, among other injuries.

Witness Kristen Taffie told 10News, "Like a normal day and all of a sudden it just went 'boom.'"

Deputies closed a stretch of the street near the intersection of Avenida Apolinaria and cleared people out of houses around the driveway where the damaged vehicle was parked, authorities said. The evacuees were sent to nearby Hillsdale Middle School, but were able to return home late Thursday evening.

Neighbor Ashlee Alfonso said, "I heard a loud boom and I heard a lady start screaming, and I looked out the window and I saw her rolling on the ground ... she jumped out of the car and it was still rolling, so it rolled back and it crashed into the car behind her. I just saw glass everywhere."

Sheriff's bomb-arson investigators were called in to identify the cause of the blast and determine if the incident was a criminal act, sheriff's Lt. Mike Munsey said.

FBI and ATF agents have joined the sheriff's department in the investigation.

Jill Hoagland, the eldest of the victim's three children, told 10News her mother was leaving work for the day at Hug-A-Ted Day Care when the incident occurred.

"It's a huge blessing and just a bizarre thing to have happened," Jill Hoagland said.

The family considers the incident a blessing because on most days Jill Hoagland's 3-year-old son, Eli, would have been with his grandmother.

"Usually my son goes to day care with my mom," Hoagland told 10News.

She said she happened to have the day off and took her son to the zoo, which possibly saved his life.

Hoagland said she still isn't clear if what happened to her mother was an accident or intentional.

"I have no idea why anyone would want, have any reason to harm her or anyone in my family that way," she said.

Even though her mother is seriously hurt, Hoagland realizes how much worse it could have been.

"I'm considering all of the blessings in this, that my son wasn't there and as far I've heard, she was conscious and she was coherent when this happened," Hoagland said.

Earlier this month, a pipe bomb was thrown out of a car on Vista Grande Drive, which is two blocks from where the woman lives.

In the Sept. 8 incident, the pipe bomb discovery prompted the evacuation of 60 residents. The bomb was destroyed by authorities and no arrests were made in the case.

10News asked investigators about a possible connection, but they would not comment on the possibility.

10News learned Hoagland and her husband filed for bankruptcy in March and had a bankruptcy hearing earlier this week.

It is not known if the bankruptcy and the explosion are related.