18 troopers of the force were injured in the accident which took place at around 6:20 AM when they were on way from Jharoda Kalan camp to Dwarka camp, police said.
Three of them slipped into coma and are being treated in the ICU.
The bus was hit by the truck from left at an intersection between Sector-14 and Sector-16 in front of National University of Law in Dwarka Sector-14.
Soon after the incident a call was made to the police. Meanwhile, by that time, a PCR van which was patrolling nearby reached the spot and rescued injured and rushed them to nearby hospitals with the help of locals.
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Assistant Sub-Inspector Ramkala (45), Head Constable Seema (38) and Saroj (40) died during the treatment while 18 of their colleagues, 16 of them women, were injured in the mishap.
"All the CRPF personnel belonged to the 88 battalion of the force. They were going to Dwarka camp to check their duty chart, following which they would have gone for deployment in the New Delhi area," a senior CRPF official said.
The errant driver of the truck, which bore Rajasthan number, managed to flee from the spot. The truck has been impounded and police have registered a case on the complaint of the driver of the bus at Dwarka North Police Station.
Efforts are on to nab the errant driver, police said.