Security has been stepped up at nurseries following warnings about two attempted child abductions.
Parents and nursery staff were sent email and text alerts this week claiming two teenage girls tried to snatch toddlers outside a Tube station and a supermarket.
Police are urging people to be vigilant while they try to trace the source of the reports.
The messages say that one or two women, aged between 16 and 19, tried to distract a toddler's guardian outside Northfields station in Northfield Avenue before trying to snatch the child.
It allegedly follows a similar attempt outside Lidl in Uxbridge Road, Hanwell.
The manager of the Iplay and Learn Day Nursery in Northfield Avenue said extra precautions had been put in place after the warnings were sent out.
And Kezi Kaymakam, deputy manager at Little Angels Nursery in West Ealing, said: "We're not taking any children out on day trips at the moment because we don't want to take any chances."
A 40-year-old mother whose child attends Little Angels said: "My sister and I are fraught with worry. It's bad enough if it's someone going round scaremongering but if it's not then it's scary and people do need to be warned."
Ealing Council will not send out an official warning until police confirm the reports.
Superintendent Ian Jenkins said: "There is no evidence to confirm such activity taking place.
"We always stress the importance of being vigilant, however we would like to appeal to residents not to be influenced by those unconfirmed claims."
Anyone with information should call Ealing Police on 0300 123 1212 or Crimestoppers, anonymously, on 0800 555 111.