The giant consumer electronics show CES has suffered a power cut, plunging part of the event into darkness.
The Las Vegas Convention Center (LVCC)'s central hall went dark at around 11:20 local time (19:20 GMT).
Two hours passed before the organisers said that the electricity supply had been restored.
They blamed an earlier downpour for causing the blackout, which resulted in attendees being evacuated from the building.
The affected space hosts booths for LG, Samsung and Sony among others.
BBC reporters at the scene said that security guards had also prevented people from entering the LVCC's North Hall, where car-makers including Toyota, Nissan and Ford have exhibits.
The Consumer Technology Association, which runs the event, has thanked visitors for their patience. But some have expressed frustration at having missed meetings.
The power failure followed heavy rain on Tuesday, which had forced Google to shut one of its booths located in the LVCC's car park.
It had been the city's first rainfall in 116 days, and had marked the wettest January day on record for the area, according to the Las Vegas Review Journal newspaper.
One LVCC employee, who asked not to be named, said that the water had affected the "trunk lines" that carry power to the venue.
The CTA later issued the following statement, which was released in conjunction with the utility firm NV Energy and the Las Vegas Visitor and Convention Authority.
"A preliminary assessment indicates that condensation from heavy rainfall caused a flashover on one of the facility's transformers," it said.
"We are grateful to NV Energy for their swift assistance, to our customers and their clients for their patience and to the staff for ensuring the safety and security of all attendees and exhibitors."
The trade fair is marketed as the "world's gathering place for all those who thrive on the business of consumer technologies".
CES sprawls across many venues close to the Las Vegas Strip, and the CTA had highlighted that most of them had been unaffected.
By Dave Lee, Las Vegas
At an electronics show, electricity is key.
As I write this, the cause of the blackout is not known. But Vegas was pelted with rain this week, and this city just cannot handle it.
Roads have flooded, hotels are leaking - including into this reporter's room - and now, potentially, this.
Embarrassing for a city that prides itself on being the best equipped for enormous shows like CES.
Patience is being tested here. This show isn't just about playing with gadgets, it's about big business. Cancelled meetings might mean deals aren't done.
I saw one delegate get irate when he was told he could not go into the main hall for his meeting.
"You ain't meeting in the dark, buddy!" the show floor worker told him.
With every passing minute, this power cut is costing a lot of people a lot of money.