Suffolk police has launched an investigation into claims of child abuse at a boarding school for troubled boys after several former pupils made assault allegations.

The inquiry was opened after a Guardian investigation into the alleged abuse at Kesgrave Hall school, near Ipswich. Ten former pupils said they suffered a series of assaults in the 1980s, including two who alleged they were sexually molested by staff.

Detectives launched an investigation on Tuesday after one of these pupils made a formal sexual assault complaint.

A spokesman for Suffolk police said: "Following a recent review of a historic child abuse investigation at Kesgrave Hall boarding school, Suffolk police have now begun an investigation into other complaints of abuse.

"To date, we aware of one new complaint but are exploring lines of enquiry that may lead to others. We are conducting a full and thorough investigation, which may include contacting those spoken to during the original investigation."

The force is also reviewing whether to reopen a 20-year-old investigation into abuse at Kesgrave Hall. Detectives interviewed at least 30 pupils in 1992 as part of the joint investigation with Suffolk social services. No charges were brought after the inquiry, which spanned several months. Four members of staff at the school were suspended and received psychiatric help.

The Tory MP Dr Daniel Poulter, whose central Suffolk and north Ipswich constituency includes Kesgrave Hall, welcomed the fresh police investigation.

He said: "I am pleased that Suffolk Police are conducting a full and thorough investigation into the alleged child abuse at Kesgrave Hall school, following my intervention.

"A number of people have written to me raising concerns about abuse when they or their family members were pupils at the school, and I would again urge anyone who has been the victim of abuse to come forward and immediately contact Suffolk police."

The Suffolk police spokesman also confirmed the force was carrying out an internal inquiry into why it initially said there were no records of the investigation, but later claimed it had discovered the files in deep storage.

The spokesman added: "We would encourage anyone who has been a victim of abuse to contact the police. We'd like to take this opportunity to reassure any victim that their complaints will be taken seriously and fully investigated."