According to a statement, the Protection Collective was expecting and prepared for a power cut, and has no intention of leaving the embassy.
The activists drew a parallel between US "attacks" on Venezuela's electric grid, and this attack on the power supply at the embassy of Venezuela.
"We are not leaving, we are going to resist," the statement says.
According to the witnesses, lights in the Venezuelan Embassy are completely out.
Earlier in the day, the Collective released a series of videos showing strange activity by police and utility workers around manholes nearby.
Police and utility doing more work at another manhole pic.twitter.com/HMGztAadOp
Earlier the Collective reported that US Veterans for Peace Director, Jerry Condon was arrested for attempting to give food to embassy protectors
For last several weeks, with the permission of the Venezuelan Foreign Ministry, the Embassy Protection Collective activist group has been living in the embassy to prevent Guaido representatives from taking it over. The activists have been holding various events like lectures and speeches inside.
In January, Guaido illegally attempted to declare himself interim president of Venezuela after disputing Maduro's reelection victory in May. Washington immediately endorsed Guaido, called on Maduro to step down and seized billions of dollars' worth of the country's oil assets.
Russia, China, Cuba, Bolivia, Turkey and a number of other countries have voiced their support for Maduro as the only legitimate president of Venezuela.
UN special rapporteurs and human rights lawyers have described US economic sanctions on Venezuela as war crimes that could lead to starvation and medical shortages.