"I believe there may be people who were in Grenfell Tower that people may not know were missing and may not have realized they were in there on the night".
Opposition politicians also say the government ignored recommendations from a 2013 review after another Londonfire killed six people.
The police chief, who went inside the charred shell of the high-rise tower over the weekend, told reporters: "I've investigated major crime for most of my service and I've seen some awful things but I don't think anything prepared me for what I was going to see when I was in there".
Cundy said the search and recovery operation in the 24-storey tower continues, and it has been incredibly distressing for families.
Late Sunday, the Metropolitan Police released three photos from inside Grenfell Tower, which showed in close detail how the fire charred the building that once housed up to 600 people in 120 apartments. Cundy said emergency workers have now reached the top of the tower.
During the visit, they met with first responders from the Emergency Services, as well as local residents and community representatives. The cause of the massive blaze is still under investigation, but anger has mounted in the community amid reports that the rain-screen cladding on the exterior of Grenfell Tower may have spread the flames.
The investigation into the fire will span a "wide range of areas", Cundy said, from its original construction, to the refurbishment and how it has been managed and maintained. "Wherever we can, we will bring people to justice if there is evidence".
Prime Minister May, criticized shortly after the blaze for failing to meet with victims, says the public inquiry looking into the tragedy will report directly to her.
There are also 78 families who have been assessed and are on course to be placed in properties that are local or in the neighbouring borough by the end of the day.
Faith leaders also called for "immediate action" to provide counselling and support services to ensure health and wellbeing to all those who are suffering, particularly the children.