By Sheila Dang, Paresh Dave and Hyunjoo Jin

(Reuters) -Hundreds of Twitter Inc employees are estimated to have decided to quit the beleaguered social media company following a Thursday deadline from new owner Elon Musk that staffers sign up for “long hours at high intensity,” or leave.

The departures highlight the reluctance of some of Twitter’s 3,000 or so employees to remain at a company where Musk earlier fired half of the workforce including top management, and is ruthlessly changing the culture to emphasize long hours and an intense pace.

Musk took to Twitter late on Thursday and said that he was not worried about resignations as “the best people are staying.”

The billionaire owner also added: “We just hit another all time high in Twitter usage…,” without elaborating.

Musk met some top employees on Thursday to try to convince them to stay, said one current employee and a recently departed employee who is in touch with Twitter colleagues.

The company also notified employees that it will close its offices and cut badge access until Monday, according to two sources. Security officers began kicking some employees out of one office on Thursday evening, one source said.

Over 110 Twitter employees across at least four continents had announced their decision to leave in public Twitter posts reviewed by Reuters, though each resignation could not be independently verified. About 15 employees, many in ad sales, posted their intention to stay at the company.

In Twitter’s internal chat tool, over 500 employees wrote farewell messages on Thursday, a source familiar with the notes said.

A poll on the workplace app Blind, which verifies employees through their work email addresses and allows them to share information anonymously, had showed 42% of 180 respondents opting for “Taking exit option, I’m free!”

A quarter said they had chosen to stay “reluctantly,” and only 7% of the poll participants said they “clicked yes to stay, I’m hardcore.”

The exact number of employees intending to leave the company could not be immediately established.

Twitter did not respond to a request for comment.

PLATFORM STABILITY

The departures include many engineers responsible for fixing bugs and preventing service outages, raising questions about the stability of the platform amid the loss of employees.

On Thursday evening, the version of the Twitter app used by employees began slowing down, according to one source familiar with the matter, who estimated that the public version of Twitter was at risk of breaking during the night.

“If it does break, there is no one left to fix things in many areas,” the person said, who declined to be named for fear of retribution.

Reports of Twitter outages rose sharply from less than 50 to about 350 reports on Thursday evening, according to website Downdetector, which tracks website and app outages.

In a private chat on Signal with about 50 Twitter staffers, nearly 40 said they had decided to leave, according to the former employee.

And in a private Slack group for Twitter’s current and former employees, about 360 people joined a new channel titled “voluntary-layoff,” said a person with knowledge of the Slack group.

A separate poll on Blind asked staffers to estimate what percentage of people would leave Twitter based on their perception. More than half of respondents estimated at least 50% of employees would leave.

Early on Wednesday, Musk had emailed Twitter employees, saying: “Going forward, to build a breakthrough Twitter 2.0 and succeed in an increasingly competitive world, we will need to be extremely hardcore”.

The email asked staff to click “yes” if they wanted to stick around. Those who did not respond by 5 p.m. Eastern time on Thursday would be considered to have quit and given a severance package, the email said.

As the deadline approached, employees scrambled to figure out what to do.

One team within Twitter decided to take the leap together and leave the company, one employee who is leaving told Reuters.

Blue hearts and salute emojis flooded Twitter and its internal chatrooms on Thursday, the second time in two weeks as Twitter employees said their goodbyes.

Notable departures included Tess Rinearson, who was tasked with building a cryptocurrency team at Twitter. Rinearson tweeted the blue heart and salute emojis.

In an apparent jab at Musk’s call for employees to be “hardcore,” the Twitter profile bios of several departing engineers on Thursday described themselves as “softcore engineers” or “ex-hardcore engineers.”

As the resignations rolled in, Musk cracked a joke on Twitter.

“How do you make a small fortune in social media?” he tweeted. “Start out with a large one.”

(Reporting by Sheila Dang in Dallas, Hyunjoo Jin in San Francisco and Paresh Dave in Oakland, Calif.; Additional reporting by Martin Coulter and Akanksha Khushi; Editing by Sam Holmes and Mark Potter)