The keys, one brass and the other silver-coloured, linked by two key rings, were found in a children's "den" in a copse where Miss King's battered body was discovered last Tuesday. Police believe they belong to her killer.
Detective Superintendent Bill Davies, who is leading the inquiry, said yesterday: "There is a very strong possibility the keys belong to the person that killed Jennifer."
He said the police werebeginning house-to-house inquiries at the homes of suspects in the Warmley area near Bristol in an attempt to find the keys' owner. He said detectives would also be interviewing a number of people for "various reasons".
Mr Davies, who is leading more than 100 officers in the inquiry, appealed for anyone who recognised the keys to come forward. The brass key is stamped on the front with Made in England and RST1A. The silver-coloured key, which is about the same length, is stamped Mr Minit on the front with the number 314 in a circle on the back.
Mr Davies said that although it had been raining heavily there was no sign of corrosion on the keys. "It would appear they have not been at the location for any length of time," he added.
Speaking at a press conference at the Warmley Community Centre, Mr Davies declined to say whether the keys bore fingerprints or when they were found.
Locksmiths, landlords, and people living in flats might be among those who could help the search, he suggested.
"If anyone came home early last Saturday morning [31 October], the day Jennifer disappeared, and was locked out and banging on the door - let us know," he added.
The body of Miss King, a 22-year-old receptionist, was discovered by police near her home at Crane Close, Warmley, on the outskirts of Bristol.
It was found in a copse a few hundred yards from the home she shared with her parents, Ray and Margaret King, both 50, her brother Andrew, 25, and sister Sarah, 11. Miss King was partially clothed and police fear she was sexually assaulted, but are awaiting the results of forensic examinations.
She was last seen alive leaving the Chasers nightclub in Kingswood at 2.03am on Saturday, 31 October, and police believe she had intended to walk the 20 minutes home.
Detectives have an unconfirmed report that a woman fitting her description was seen near her home, apparently being pestered by a man walking backwards in front of her. He is described as white, in his early twenties, of slim to medium build with short dark hair.
Detectives suspect her attacker would have got mud on his clothes and body and may have received scratches and minor injuries.
There is a pounds 36,000 reward for information leading to the conviction of her killer. Anyone with information should contact the police on 01275 818181.