A public housing resident in Tseung Kwan O has discovered that the steel-grille primary door to her flat can be opened by at least four of her fellow residents' keys. The Housing Authority said that it expected duplicate key and lock combinations to occur once in about every 2,000 locks. Stanley Tam Lanny, a district councillor for the Tsui Lam Estate, said he was informed of the situation by the resident, a Mrs Ho, last Wednesday. He said Mrs Ho had also discovered that her own two keys, one for her door and the other for the steel-grille gate, can open another resident's door and gate. The four fellow residents reside on the same floor and all five flats are in the same building, Sau Lam House, at the estate. 'The five households had their iron gates changed in 2005 and 2006 by the Housing Authority,' Mr Tam said. 'I think they were supplied with the same shipment of gates so some of their keys and locks are interchangeable.' The Housing Authority confirmed five households in the Tsui Lam Estate reported that they had found their locks could be opened by the same key. 'On request, we have changed their locks already,' an authority spokeswoman said. She said the locks were changed in 2006 when residents in the estate were allowed to buy their own flats under the Tenant Purchase Scheme. She said about 3,000 households on the estate bought their flats but the authority did not record how many locks were changed. Residents who faced similar problems could contact the authority, she said.