Toronto police are cautioning TTC riders to be mindful of their surroundings after several people were robbed of their smarthpones this month.

Sgt. Jack West says riders are getting so drawn into what's going on with their handheld devices, that they fail to notice suspicious behaviour around them.

"As the (subway) train comes into the station and it stops and those doors open, that's when you have to watch," says West.

Thieves are likely to use that opportunity to grab a rider's phone and then run out the closing doors before getting lost amongst others on the crowded platforms.

"So every once in awhile they should acknowledge their surroundings, who's sitting beside them, across from them, who's standing in the aisle," he says.

West recommends passengers keep their phones low and out of sight.

In one Toronto police division, about one smartphone has been stolen from on or near TTC property every day this month.

Potential victims can also be scoped out on transit vehicles by thieves, and then get robbed as they leave TTC property, police say.

"You may be followed off the TTC and when you get out on the street, someone may come up behind you and snatch (your phone)," West says.

In this case, West recommends people put away their phones if they suspect they're being followed and get to a safe place to call for help.