Police in India say they have detained three people in connection with Sunday's bomb attack aboard a train travelling from India to Pakistan.
The police says one detained man resembles a man in the sketch
Two men and a woman were picked up from northern Rajasthan state following a tip-off from the police in neighbouring Haryana, where the blast took place.
The blasts and blaze on the cross-border train killed 68 people.
Authorities in India say 33 of the bodies have been identified so far. Twenty-seven of them are Pakistanis.
Meanwhile, the bodies of 12 Pakistani nationals killed in the blast, including six members of one family, have arrived in Pakistan.
The three people were detained by police in Bikaner, one of Rajasthan's four districts bordering Pakistan, says the BBC correspondent in the state.
The fire engulfed two carriages on the Samjhauta (Friendship) Express
Rajasthan Interior Minister Ghulab Chand Kataria told the BBC that the police had initially detained one person, who resembled the sketch of a man put out by police on Tuesday.
The two others who had been picked up were relatives of the man, he said.
"It is too early to say anything until the interrogations are complete," the minister said.
The police are questioning the three, and would give no further details.
It is not clear who was behind the attack on the Friendship Express near Panipat, 80km (50 miles) from Delhi, and no group has admitted carrying it out.
Police say they believe the men shown in the sketches left the train just moments before the bombs went off.
However, it is not known how the two men got off the speeding train, which had only slowed down after the driver was alerted that there was fire in two carriages.
Police say they recovered 14 plastic bottles "filled with kerosene", a suitcase and plastic digital timers from the site of the blasts.
Indian and Pakistani leaders continued with scheduled peace talks this week in Delhi. Both sides condemned the blasts and vowed to continue with the peace process.
The two countries established a joint panel last year to share intelligence to help fight terrorism.
Similar attacks in the past have been blamed by India on Pakistan-based militants, but this time neither side has rushed to accuse the other.
The bombing of commuter trains in Mumbai last year effectively derailed peace talks for many months - although allegations of Pakistani involvement were never proved and vehemently rejected by Islamabad.
The twice-weekly cross-border Friendship Express - one of only two rail links between India and Pakistan - was restarted in 2004 after a two-year gap as part of the peace process.
Talks have been going on for three years, but have made little headway on key issues such as the dispute over Kashmir.