Lucknow, May 1 (IANS): The detention Monday of 40 people for trying to enter India from Nepal without valid identity papers through the border in Maharajganj has put the Uttar Pradesh intelligence unit on alert.

Such a movement was "not routine" and was an "ominous sign", a police intelligence official, who did not want to be named, told IANS Tuesday.

Sashastra Seema Bal personnel had detained the group which comprised of 11 men, seven women and 22 children at the border in Sonauli.

During interrogation, a police source said, one of the detained persons claimed that several years ago some men had crossed over to Pakistan and got married and settled there. Now they were trying to return home to India, said the source.

However, intelligence officials are not convinced with the "homecoming" theory and are probing the matter with from "all perspectives," an official said.

At least 12 of those detained are natives of various Jammu & Kashmir villages, said a senior officer at the director general of police headquarters here.

The officer said that "with subversive elements making attempts to infiltrate into India from all possible routes, including uncharted routes".

As of now, "tough and sustained questioning was on," the officer said.

J&K Police and central agencies were also helping in the investigation, the officer said.

The porous 550-km India-Nepal border, with Maharajganj acting as a crossover point, has been a matter of concern for the security and intelligence agencies.

Uttar Pradesh Chief Minister Akhilesh Yadav, during the chief ministers' meet on internal security in New Delhi on April 16, had asked the union home ministry for integrated check posts, similar to the one set up between India and Pakistan at Attari-Wagah, at the border to check movement of "subversive elements".