SAN JOSE, Calif. | E-commerce site eBay is asking users to change their password after a cyberattack compromised a database containing encrypted passwords.

The company says there is no evidence of any unauthorized activity and no evidence any financial or credit card information was stolen.

EBay says its investigation is active and it can't comment on the specific number of accounts affected, but says the number could be large, so it is asking all users to change their passwords. EBay had 145 million active users at the end of the first quarter.

Cyberattackers stole a small number of employee log-in credentials that gave access to eBay's corporate network, the company said. The San Jose, California-based company is working with law enforcement to investigate the attack.

The database was hacked sometime between late February and early March, but compromised employee log-in credentials were first detected two weeks ago.

EBay owns electronic payment service PayPal, but eBay says there is no evidence PayPal information was hacked, since that information is stored separately on a secure network.

The attack follows several other high-profile hacking incidents, including a massive data breach at Target stores and the spread of the computer security flaw nicknamed "Heartbleed." Heartbleed took advantage of a flaw in a key piece of security technology used by more than 500,000 websites that had been exposing online passwords and other sensitive data to potential theft for more than two years.

And during the Target credit data breach last year, hackers stole about 40 million debit and credit card numbers and personal information for 70 million people.

Shares of eBay Inc. fell 31 cents to $51.65 in morning trading.