A woman is dead and another has serious injuries after a stabbing at High Park subway station on Thursday afternoon.

Toronto police said they received a 911 call shortly after 2 p.m. about a man armed with a knife on a train.

Initial reports suggested that the incident occurred on the eastbound platform.

When officers arrived, they located two women suffering from stab wounds.

Toronto paramedics said they rushed the victims to hospital – one in life-threatening condition and the other in serious condition.

In a subsequent update, Duty Insp. Lori Kranenburg said one of the women had been pronounced dead. She added that the other victim's condition is now stable.

Kranenburg said a man was taken into custody at the scene.

"It's too early at this point in time in the investigation to know whether or not the parties were known to each other," she said.

When asked what led to the stabbing, Kranenburg said police do not yet have information on the circumstances surrounding the incident. She noted that there is no threat to public safety.

"As part of the investigation, video will be reviewed and hopefully that will provide some clues as to what occurred. There were a number of witnesses present at the time. Some have stayed and provided statements to police," she said, urging anyone who has not yet spoken to police to come forward.

In a statement, the TTC said Rick Leary, the chief executive officer, spoke to the Toronto police Chief James Ramer and offered his full support to the investigation.

"Safety of customers and employees is paramount to all the TTC does," the statement read.

"The TTC moves hundreds of millions of customers every year without incident, but is constantly looking at ways to improve safety."

The transit agency said additional special constables and uniformed staff were placed across its system to reassure customers. In addition, the statement highlighted some of the safety features and programs the TTC has put in place, which include adding more cameras and more visible staff to deter criminal acts.

Speaking to CP24 on Thursday afternoon, TTC spokesperson Stuart Green said the agency is concerned and shocked about the incident and called it unacceptable.

"We talk about safety being paramount to all that we do. And that's our commitment to both our customers and our employees. So on days like today, we understand that people feel a little shaken," Green said.

"Our response is to put more staff out there to make sure that people have an extra sense of comfort today.

He said the TTC will keep working to minimize violent incidents and make the system safe for its riders, including continued dialogue with the city, Toronto police and mental health support services.

Toronto Mayor John Tory said in a separate statement that he plans to meet with TTC officials and police to discuss further safety measures that could be implemented to prevent a similar incident from happening again.

"Like all Torontonians, I was shocked to hear about the fatal stabbing at High Park station this afternoon. We can never accept acts of violence of this kind happening anywhere in our city," Tory said.

"My thoughts are with the family and friends of the woman who has lost her life. We hope for the quick recovery of another woman who is in hospital with injuries."

Shuttle buses are running between Keele and Jane stations as subway service has been suspended on that portion of Line 2 following the stabbing. The TTC noted that shuttle buses are not stopping at High Park Station due to the incident.

The stabbing is the latest violent incident on the TTC this year. In June, a woman died after being set on fire while on a TTC bus at Kipling Station. In April, a woman was pushed onto the tracks at Bloor-Yonge Station and suffered a broken rib. She has since sued the transit agency.

Toronto police said they would increase their visibility on the TTC following a string of violent incidents earlier this year.

TTC employees have also been attacked several times this year, with the most recent incident earlier this week when a female operator was assaulted and robbed while on duty.

The attack prompted the Amalgamated Transit Union (ATU) Local 113, which represents transit workers, to call on the TTC to do more "to prevent all forms of violence towards transit workers."

The union released a statement following the stabbing, reiterating their demand for action from the TTC and the city.

“ATU Local 113, along with the citizens of Toronto, are outraged at these repeated acts of violence on public transit and demand that the #CityofToronto and the #TTC take transit safety seriously and now act with urgency,” the statement read. “Waiting is not an option."