18/09/2014 07:29 BST | Updated 18/09/2014 12:59 BST

Alice Gross Missing: Suspect Arnis Zalkalns Is A Convicted Murderer

A Latvian builder being sought in connection with the disappearance of schoolgirl Alice Gross is a convicted murderer, detectives have revealed.

Fourteen-year-old Alice was last seen on August 28, when she was spotted on CCTV by the Grand Union Canal in west London.

Detective Superintendent Carl Mehta, from the Met's Homicide and Major Crime Command, today named Arnis Zalkalns as a suspect after he was seen on CCTV around the tow path where Alice went missing.

Suspect Arnis Zalkalns was convicted of murder in Latvia, detectives have revealed

Mr Mehta said that the 41-year-old had been convicted of murder in his country and was also arrested on suspicion of indecent assault in the Ealing area in 2009.

The officer said: "The conviction was in 1998 and he served a custodial sentence of seven years."

Mr Mehta said no further action was taken against Zalkalns over the indecent assault allegation, which involved a 14-year-old girl.

He also insisted that police have no evidence suggesting Alice has come to harm.

Alice Gross disappeared on 28 August

"This is not a murder inquiry in the sense that we don't have any evidence or information to say that Alice is not alive," Mr Mehta said.

Zalkalns was seen on CCTV cycling along Brentford Lock at 4pm on August 28, 15 minutes after Alice walked the route.

Detectives believe he is likely to have seen Alice as they were both going north along the canal towpath.

Since Zalkalns was last seen at his home in Ealing on the evening of Wednesday September 3 he has not accessed his bank account or used his mobile phone. His passport was left at his house.

His friends and family have told police that his disappearance is out of character.

CCTV stills of Zalkalns cycling along Brentford Lock 15 minutes after Alice walked the same route

Mr Mehta said Scotland Yard was liaising with authorities in Latvia but Zalkalns is not thought to be wanted by police there.

Asked if he posed a threat to the public, the officer said: "I think given what we are finding out about his antecedents and his history, clearly he potentially poses a risk to the public.

"I would ask if anyone sees him not to approach him but to immediately dial 999 and contact the police."

A reward of up to £20,000 is being offered for anyone who has information that leads detectives to find Alice.

Mr Zalkalns is described as white, 5'10", of stocky build and with dark brown hair that he normally wears tied in a pony tail. He is thought to be from Riga, the Latvian capital.

He rides a red Trek mountain bike and was reported missing by his partner at midday on Friday, September 5.

Forensic searches are being carried out at his home address.

Mr Mehta thanked the public for their "support and help" as detectives try to find the 14-year-old anorexic schoolgirl.

He said: "This remains an investigation focused on finding Alice, clearly we are also seeking Arnis in respect of her disappearance and we urgently need to find him and question him about that.

"We have no evidence that Alice is not alive and no evidence that Alice has come to harm. However, all lines of inquiry remain open at this point."

A 25-year-old man arrested on suspicion of murder on September 6 was told he faces no further action.

A 51-year-old man, who was arrested by officers on suspicion of murder on September 7, was released with no further action the following day.

Alice's last known movements were between 1pm when she left her Hanwell home and 4.26pm when she walked along Trumpers Way, towards Hanwell.

Her Vans rucksack was found by the River Brent a week and a half ago, but no money or purse was inside and her white iPhone 4S with a distinctive cracked case has yet to be found.

Officers have said her missing smartphone may hold "key" information about her disappearance. The device last connected to the network at just after 5pm on August 28.

A couple saw Alice's bag on August 28 at about 8.15pm on the footpath that runs besides the River Brent between Hanwell Bridge and the Grand Union Canal.

No evidence has been found to suggest she was bullied on social media but hoped finding her phone might uncover any secret communications she might have had.