4,000 litres of chemicals spilled into Walsall canal
An investigation is ongoing after 12 miles of canal was affected by the spill.
The Environment Agency has confirmed that around 4,000 litres of toxic chemicals were released into a canal in Walsall.
Around 12 miles of the canal network had to be closed off after the chemical spill on Monday.
The majority has now been reopened, after testing showed water quality is within safety guidelines.
A stretch of the Walsall Canal, about a half mile long between James Bridge on Bentley Mill Way in Darlaston, and Rollingmill Street, Walsall, remains closed.
Walsall Council said in an update on Friday: "Laboratory testing conducted by the Environment Agency has resulted in the reopening of sections of the canal in Walsall and neighbouring areas which have been closed following a chemical spillage.
"Thorough testing has taken place within a 12-mile stretch of the canal from the Walsall lock flight to the lock flights at Rushall/Ryders Green and Perry Barr."
In order to avoid potential health risks to the public and to their pets, stretches of canal and towpaths have been closed since Monday.
Lab testing shows that water quality is within public health guidelines in significant stretches of the canal that had previously been closed.
Previous tests had shown elevated levels of chemicals, including sodium cyanide and zinc cyanide.
The council's statement added: "The Canal & River Trust has arranged safe passage for boaters who wish to leave the area and is working to reopen the canals to navigation outside the restricted area as quickly and safely as possible.
"Our priority continues to be the safety of our residents and canal users. Local, regional and national agencies are working together to minimise the potential risk to health following the spillage."
The Environment Agency (EA) is investigating a company following what it termed an "unacceptable" incident and warned it would take "robust enforcement action" if any wrongdoing had occurred.
In a statement issued on Wednesday, the EA said it was investigating Anochrome Ltd, where it believes the spill of sodium cyanide originated.
Anochrome said it had immediately notified the EA and Severn Trent Water following the incident and its senior management team remained on-site working to minimise and contain the spill.
In a statement, it said: "We can confirm that a chemical incident occurred at Anochrome Ltd Walsall in the early hours of Monday August 12. Regrettably, as a result, some of the released chemicals entered a canal in Walsall.
"Our immediate response was to notify the Environment Agency and Severn Trent Water. Our senior management team has been - and remain - on-site working collaboratively with all relevant authorities and agencies to minimise and contain the spill."