Popular video game site Roblox had begun to restore service Sunday after a two-day outage that left millions of players without access to the online game world over the Halloween weekend.

"We have identified root cause and solution," the California-based collaborative platform tweeted, adding it was "working on getting things back online."

By Sunday afternoon, Roblox said it was "incrementally bringing regions back online," after the site had been down since Friday.

The Roblox website displays a message banner that reads: "We're making things more awesome. Be back soon."

In a statement to The Verge magazine, Roblox said its website was not down due to an "external intrusion."

"We believe we have identified an underlying internal cause of the outage with no evidence of an external intrusion," a spokesperson said.

With its Lego-like avatars and easy-to-learn coding for budding programmers, the online gaming app has become a thriving clubhouse for young gamers, most of them no older than 16.

The Roblox platform currently boasts some 33 million users.

Roblox also pays its game creators, both aspiring and more advanced, through micro-transactions.

The gaming site went public on Wall Street in march at $70 a share and was worth $84 at the close of trading on Friday, for a market capitalization of $48 billion.