IRWINDALE (CBSLA.com) — Twelve people, including a pregnant woman, were injured Tuesday morning in an accident involving a van and a cement truck.

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The accident happened on the 605 Freeway at Arrow Highway in Baldwin Park around 10:12 a.m., the Los Angeles County Fire Department said.

The truck was entering the freeway when it went down an embankment, crossed all four lanes of traffic and collided with a van before slamming into the center divider.

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Approximately 30 gallons of diesel fuel spilled when the truck overturned, blocking the one, two and three lanes for several hours.

All lanes were later reopened.

Three people were transported to a local hospital in critical condition, while nine others were transported with unknown injuries.

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The accident was under investigation.