Subway service was disrupted for two hours on the west end of the Bloor subway line Friday morning due to an "act of vandalism" to signalling equipment in the tunnel near Royal York Station.

Service was halted between Kipling and Jane stations at about 10 a.m. Friday so police could investigate and TTC staff could complete some repairs, TTC spokesperson Stuart Green told CBC Toronto on Friday morning. Service resumed around noon.

ALL CLEAR: The delay at Royal York Station has cleared. Regular service has resumed on Line 2. <a href="https://twitter.com/hashtag/TTC?src=hash&ref_src=twsrc%5Etfw">#TTC</a> —@TTCnotices

TTC executive director for corporate communications Brad Ross said 72 shuttle buses were operating between Jane and Kipling stations. He had earlier tweeted that riders could also use GO and the UP Express with proof of TTC payment.

According to Ross, a train operator first noticed signal problems near Royal York station around 5:25 a.m. Crews went into the tunnel and found that a piece of signalling equipment had been vandalized, Ross told CBC Toronto. He would not get into the nature of the vandalism, or explain how vandals were able to access the tunnel.

None of the "failsafe mechanisms" in place were compromised, he added, so subway service could continue through the morning rush hour before it was shut down for the police probe.

"Nevertheless, we are going out and surveying other equipment around the network to make sure that no other damage has occurred elsewhere," Ross said Friday afternoon. Also, he added: "We have an increased presence over the next several days of our special constables."

TTC staff have been asked to "remain vigilant" for "anomalies in the system," Ross said. As well, he appealed to riders to tell TTC staff or police if they see something unusual.

Toronto police Const. Jenifferjit Sidhu said earlier Friday that police were in the tunnel during the closure to take photographs and pull surveillance video in order to determine a timeline for the incident and identify suspects.

Ross said the TTC will share all surveillance video with investigators.