(Corrects to Wednesday from Tuesday in last paragraph)
MEXICO CITY, Nov 14 (Reuters) - A cyberattack on computer networks of the Mexican national oil company Pemex is "totally under control" and did not have any negative consequences, Security Minister Alfonso Durazo said on Thursday.
The attack was first detected on Sunday and over several days since has halted some administrative work, including the processing of payments, but Pemex said its oil and gas operations were not harmed.
Durazo, speaking with reporters, described the impact as "without consequences." An investigation into the hack was underway, he said.
While Durazo sought to minimize the impact, several Pemex employees said, however, that operations were still not up and running as usual.
Finance Minister Arturo Herrera said the attack did not hit systems that store confidential information, but only the personal computers of some employees.
"It's a warning that we have to be careful with all our information," said Herrera.
In one Pemex office building, entire floors of computers were wiped out, said one worker who spoke on condition of anonymity, adding, "We're still not operating normally."
Another Pemex employee, who was also not authorized to speak to reporters, said networks remained down and some workers had resorted to using old laptops to "half-way work."
Energy Minister Rocio Nahle said on Wednesday that Pemex would not pay a ransom demanded by the suspected hackers. Hackers have told Reuters they demanded about $5 million in bitcoin from the firm, which is struggling to pay down massive debt, reverse years of declining oil output and avoid further downgrades to its credit. (Reporting by Daina Beth Solomon, Adriana Barrera and Sharay Angulo; Editing by David Alire Garcia and Grant McCool)