The private bus, proceeding to Hyderabad from Bangalore, caught fire after hitting a culvert around 5.20 a.m. near Palem in Kottakota mandal, about 150 km from here.
Besides the driver and cleaner, only five passengers escaped the horrific disaster. The injured passengers were shifted to a hospital. The driver and cleaner, who escaped unhurt, are being questioned by police.
Flames engulfed the bus in no time as the diesel tanker burst after hitting the culvert, Mahabubnagar Superintendent of Police Nagendra Kumar said quoting witnesses.
Initially, there was confusion on the number of passengers in the bus.
Transport Minister Botsa Satyanarayana told reporters in Hyderabad that 45 people were killed.
He said the Volvo bus, belonging to Jabbar Travels, had a capacity for 43 passengers but was carrying 50 people.
The passengers were asleep when the accident took place, leaving no time for them to escape. The victims were charred beyond recognition.
People from nearby village said the bus was reduced to ashes within minutes. The first ambulance reached nearly an hour later.
According to one of the survivors, some people broke the windows to jump out. But others were not lucky. He said the door was also locked, leaving no escape route for most passengers.
Preliminary investigation by police revealed that speeding caused the accident. The transport minister said there was no speed limit for Volvo buses.
Botsa said the bus was registered in Anantapur district in the name of Diwakar Road Lines and Jabbar Travels had taken it on lease.
Police detained the manager of Jabbar Travels in Hyderabad and took him to Mahabubnagar for questioning.
Nagendra Kumar said a list of only 29 passengers was received from the private bus operator. Other passengers are believed have boarded the bus at Hindupur and Anantapur.
The bus left Bangalore at 10 p.m. Tuesday and was scheduled to reach Hyderabad at 6.30 a.m.
Policemen and forensic experts retrieved the charred remains of the passengers and keeping them under a tent put up near the scene on the Bangalore-Hyderabad highway.
The forensic experts, from Hyderabad, will conduct DNA tests to identity the bodies.
Heartrending scenes were witnessed at the scene as rescue workers found the body of a child on a mother's lap. Both were charred.
Police have identified three victims.
Mahabubnagar District Collector M. Girija Shankar said five passengers were shifted to the DRDO Apollo Hospital in Hyderabad.
Anxious relatives of some of the passengers rushed to Jabbar Travels office here for information. However, the private operator did not have the list of passengers and other details.
Chief Minister N. Kiran Kumar Reddy directed the district collector and superintendent of police to conduct a thorough investigation.
Prime Minister Manmohan Singh as well as Kiran Reddy and other political leaders of Andhra Pradesh expressed shock and anguish over the deaths.
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