Kolkata, Jul 19 (IANS): Railway Minister Mamata Banerjee Monday said there was "some doubt" over the West Bengal train accident in which at least 49 people were killed.

The speeding Sealdah-bound Uttar Banga Express rammed into the stationary Bhagalpur-Ranchi Vananchal Express from the rear at Sainthia station in West Bengal's Birbhum district early Monday morning.

Banerjee told reporters while leaving for the accident site: "We have some doubt in our mind. We are searching for information. Let us now find details."

Describing it as "a sad incident", she said: "Human lives are very important."

The minister said: "We are really sorry for this. Sorry to see two incidents take place in West Bengal in two months."

"Whatever happens is not (a) casual thing. We will take necessary action. We will take strong steps whoever is behind this."

On May 28, 148 people were killed when the Mumbai-bound Gyaneshwari Express derailed following Maoist guerrillas sabotaging the tracks near Jhargram in West Midnapore district. A speeding freight train then rammed into the derailed coaches.