The 14-year-old disappeared four weeks ago, walking along the Grand Union Canal in west London.
Police are also looking for a Latvian man, Arnis Zalkalns.
Alice disappeared on 28 August but Newsbeat understands there are at least four other teenagers missing in the UK in the same time period.
It sounds like a big number but figures show 140,000 under-18s are reported missing in the UK each year.
Of course, most are found within days.
Here are some of the cases on the charity website Missing People.
Police are concerned for Demi Collins who is 16 and was last seen in Woolwich, south-east London on the 8 September and in a separate missing persons case, Jo McFarlane-Hills, aged 13, was last seen in Lancing in West Sussex on 22 September.
On the Missing People website there are 37 under-18s currently classed as missing children, including Alice.
She was last seen in Hanwell, Ealing, west London.
But there is also another girl who disappeared from London this month, Chelsea Abraham, 15, who was last seen on 8 September.
Also known to have gone missing is Shane Crawt, 15, who disappeared in Slinford, Sussex on 17 September.
The Missing People charity hopes posters, which can be printed off, from its website and police appeals will help to find these missing teenagers.
A spokesperson said the idea is that people are more likely to come home or turn themselves into a charity rather than the police.
The website carries the following message: "We are here for you whenever you are ready; we can listen, talk you through what help you need, pass a message for you and help you to be safe. Call. Text. Anytime. Free. Confidential. 116000."
Out of all these teenagers who have not been seen, Alice Gross is the only case to have prompted a widespread police investigation.
The hunt for the 14-year-old is now being described as the largest police search operation since the 7/7 bombings (2005) and it is hoped this latest staged reconstruction by police will help answer the many questions about what happened and her whereabouts.
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Police searching for missing schoolgirl Alice Gross have staged a reconstruction of her last known movements.