The quake rocked downtown Mexico City, located about 190 miles northeast of the epicenter..

Initial reports from a reporter tweeting in the capital said the quake lasted for as long as 40 seconds in the capital, where where office workers streamed into the streets. There were no immediate reports of injuries or damage.

The Pacific Tsunami Warning Center said initial indications find no tsunami threat to Hawaii.

The USGS downgraded the magnitude of the quake from an initial 6.8 to 6.4.